chore: add fitz to mypy ignore_missing_imports overrides

PyMuPDF (`fitz`) has no type stubs, so mypy's import-not-found fails on
any edit to files importing it (commands/board/view.py,
kicad_interface.py). Same treatment as the existing pcbnew/kipy/PIL
entries. Needed so the export-tool commits on this branch pass the mypy
pre-commit hook independently.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -33,6 +33,7 @@ module = [
     "cairosvg",
     "sexpdata",
     "skip",
+    "fitz",
     "kipy",
     "kipy.*",
     "schematic",